UIButton Text Margin / Padding

You can also set the inset values from the Interface Builder Size Inspector inside a Storyboard or xib.

// Swift
var titleEdgeInsets: UIEdgeInsets!

// Objective-C
@property(nonatomic) UIEdgeInsets titleEdgeInsets;

Use this property to resize and reposition the effective drawing rectangle for the button title. You can specify a different value for each of the four insets (top, left, bottom, right). A positive value shrinks, or insets, that edge—moving it closer to the center of the button. A negative value expands, or outsets, that edge. Use the UIEdgeInsetsMake function to construct a value for this property. The default value is UIEdgeInsetsZero.

https://developer.apple.com/documentation/uikit/uibutton/1624010-titleedgeinsets

Setting the content insets will prevent the UIButton's title to shrink or truncated, giving the text margin a padding.

In Swift 4, note the use of contentEdgeInsets not titleEdgeInsets:

btn.contentEdgeInsets =  UIEdgeInsetsMake(8, 8, 8, 8)
btn.titleLabel?.lineBreakMode = .byWordWrapping

That will make the button wrap its text and keep it one line as long as there is a space for it + adding some padding around

The challenge with the accepted answer is that setting the titleEdgeInsets is the limitation, as noted in Apple's documentation:

This property is used only for positioning the title during layout. The >button does not use this property to determine intrinsicContentSize and >sizeThatFits(_:).

This means that setting the margins only works if the button is explicitly sized to fit the title label and the margins. If a title is too long or the margins too large, the title text may be clipped. This is OK for a button whose title you know at compile time, but for a variable length button title, can pose a problem.

An alternate approach accommodating variable title length is to leave the titleEdgeInsets as the default value. Once the button's title is set, add explicit width and height constraints that accommodate the button's title label and the additional margins. For example:

let margin: CGFloat = 10.0

let button = UIButton()

button.setTitle("My Button Title", for .normal)

button.widthAnchor.constraint(equalToConstant: button.titleLabel!.intrinsicContentSize.width + margin * 2.0).isActive = true

button.heightAnchor.constraint(equalToConstant: button.titleLabel!.intrinsicContentSize.height + margin * 2.0).isActive = true

Position the button without adding further height or width constraints and it will appear properly regardless of title length.